One of the simplist ways for carrying a set of lock keys, e.g. for opening Yale locks and other key-operated locks, is to thread the keys onto a split ring. For this and allied purposes, the typical key of this type has a hole in its handle portion which extends completely through the thickness of the key. Thus a set of keys may be kept together in a pocket or purse, or worn, e.g. on a belt loop. Sometimes non-key items are carried on the same split ring with a set of keys; e.g. a charm, a fingernail-clippers, a small screw driver and/or a relatively large decorative shield, tag, advertising sign or the like may be carried on the ring with the set of keys. The typical split ring is a tight spiral of brass, spring steel or equivalent synthetic plastic material, which extends through one complete helical turn, and a fraction of a second helical turn, e.g. from about one-tenth to about nine-tenths of a second helical turn.
Thus each end of the split ring lies axially adjacent an intermediate portion of the split ring and in order to thread a key onto the ring or off the ring it is necessary to temporarily, elastically force the respective split ring end axially away from the respective split ring intermediate portion. The typical split ring is approximately one and a quarter inches in diameter (although many sizes are used) and the typical key is approximately one and a half to three inches in length. Usually the hole in the handle portion of the typical key is about one-eighth inch from the rear end of the key and is circular, rounded-triangular or oval in shape, measuring about three-sixteenths inch across. Thus, when the typical key is mounted on the typical split ring key holder, the key blade is too long, and the hole in the key handle is too small, to permit rotation of the key through the central opening of the key ring.
There is a limit to the number of keys that can be carried on such a key ring; as more keys are slipped onto the ring it becomes increasingly more difficult to spread the split far enough apart to slip on one more key.
When slipping a key onto or off of a split ring key holder, the task of spreading the split axially open in order to start the slipping may be difficult, especially where the ring contains nearly a capacity complement of keys and the like and/or where the ring is made of especially stiffly resilient material and/or whether the user has less than average strength or dexterity in his or her hands and/or where the key to be slipped onto or off the ring is a thick one and/or the respective end of the key ring and the site on the key which must interact with it to open up the split gives little purchase.
A way that this latter problem has been addressed in the prior art is to provide a special site on the ring where the key to be mounted can be wedged into the split to open up the split. Typical solutions of this type are shown in the prior U.S. patents of Kirby, U.S. Pat. No. 932,787 issued Aug. 31, 1909, Korns, U.S. Pat. No. 1,462,205 issued July 17, 1932 and Becker, U.S. Pat. No. 603,247 issued May 3, 1898. Most of these prior art solutions are more effective when the user wants to slip a key onto the ring than when they want to slip a key off the ring. Furthermore, use of those inventions requires use of particular, somewhat unusually-shaped split rings that may not be widely available. The fact remains that most split ring key holders in use are plain and do not have built-in wedging provisions so there is a need to facilitate wedging open plain split key rings.